MATHEMATICAL MODEL FOR PREDICTION OF ALPHA ACID CONTENTS FROM METEOROLOGICAL DATA FOR 'SAAZ' AROMA VARIETY

Abstract

Significant influence of weather conditions on alpha acid contents in hop cones is generally accepted. Long-term monitoring of alpha acid content in hops cultivated in the region of central Europe shows notable year to year differences. Mathematical models of the relationship between alpha acid content and meteorological parameters were worked out for 'Saaz' aroma variety using data covering the years 1981-2006. Mean alpha acid content was determined by lead conductance method (EBC 7.4, toluol). Meteorological data were provided with CHMI (Czech Hydrometeorological Institute) observatory in Doksany located approximately 2 km from the farm. Using multi-linear regression, a ten parameter model has been outlined. Average temperatures from July and August, average air humidity from June, July and August, average daily sunshine duration from June, July and August and accumulated precipitation from August have been found as key input variables of the model. Correlation coefficient of the relationship between predicted and actual alpha acid contents is r=0.914, coefficient of determinancy r 2 =0.835. The model showes that alpha acid content in 'Saaz' aroma hops is influenced by weather conditions in a relatively short time period June-August, i.e. stage of flowering, cone forming and ripening. July temperatures are the most significant weather parameter (r i =-0,24) effecting alpha acid contents in 'Saaz' hops confirming empiric experience.